The present invention relates to an apparatus for slitting a moveable web of corrugated paperboard and, more particularly, to a lubricator system that uses Teflon or other suitable lubricant pucks or blocks that are physically pinched or loaded onto a slitting blade to assist in sharpening of said blade and to prevent build-up of starch or similar adhesive associated with the production of the corrugated paperboard.
A slitter/scorer is used on the dry end of a corrugator to slit and score the corrugated web emerging from the double backer so as to create multiple independent “outs” that can be routed to the upper or lower level of a cutoff knife. The knife then cuts these “outs” to designated lengths to create the independent sheets that are then stacked. The slitting tool used to slit the web is a thin blade of approximately 1-2 mm in thickness that rotates at high speed with the corrugated web supported below the blade by a rotating solid anvil as described in U.S. Pat. No. 5,090,281, the disclosure of which is incorporated by reference herein.
The web that is slit is formed in and emerges from an upstream double backer with a green bond of the starch adhesive on the lower liner that has a propensity to adhere to the thin slitting blade. A standard approach to prevent starch from building up on the thin blade involves wiping a lubricating fluid onto the blade using a wick lubricator pad. A pressurized oil feed is used to wet the wick. The wick is replaced at frequent intervals to insure a fresh surface free of starch accumulation.
There are several problems with this conventional approach to thin blade lubrication. First, there is potential for over lubrication and wetting of the wicks that can result in dripping of lubricant onto the top of the board, particularly at corrugator stop. Also, to the extent that the wick wipes the lubricant on the blade, this same lubricant can contaminate the edges of the corrugated board.
To address this issue and to make this problem acceptable to corrugated manufacturers who are manufacturing board for food-grade applications, a food-grade acceptable lubricant is necessary. This is expensive and not universally acceptable. Also, the food-grade lubricant works less well than, for example, a WD-40 type lubricant. Another problem is associated with the pumps and valves and lubricant lines that have to be routed to the slit blades resulting in a complicated and maintenance-intensive system. Lubricant must be stirred to prevent coagulation. Valves become stuck. Lubrication pads need to be changed on at least a daily basis and this is expensive and labor intensive.
A recently introduced solution to the lubrication problem involves use of a polytetrafluoroethylene (PTFE) block as an anvil. This concept is described in U.S. Patent Application Publication US2006/0075864 A1 with publication date Apr. 13, 2006. The thin slitting blade plunges into the anvil and the PTFE block then lubricates the blade as it rotates in the PTFE support. As the blade wears away the PTFE, the blocks can be laterally shifted to create a new PTFE wear block.
This solution to lubrication creates a problem on long runs between order changes where the PTFE wears. Without an order change, it is not possible to shift the block to solve the wear issue. Also, the constant lateral feeding of PTFE blocks into the machine is labor intensive and is not routinely done by plant operating personnel. As the thin blade is plunged into the PTFE block, it works effectively, but as it wears, the effectiveness of the lubrication rapidly decreases.